ci: Introduce a util module

With the gradual rewrite of the Makefile to the 'helper' script will
require helper functions that would better live in a separate util
module.

Signed-off-by: Erik Skultety <eskultet@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>

ci/util.py

@@ -0,0 +1,40 @@
+import json
+import urllib.request
+import urllib.parse
+
+from typing import Dict, List
+
+
+def get_registry_uri(namespace: str,
+                     gitlab_uri: str = "https://gitlab.com") -> str:
+    """
+    Construct a v4 API URI pointing the namespaced project's image registry.
+
+    :param namespace: GitLab project namespace, e.g. "libvirt/libvirt"
+    :param gitlab_uri: GitLab base URI, can be a private deployment
+    :param api_version: GitLab REST API version number
+    :return: URI pointing to a namespaced project's image registry
+    """
+
+    # this converts something like "libvirt/libvirt" to "libvirt%2Flibvirt"
+    namespace_urlenc = urllib.parse.quote_plus(namespace)
+
+    project_uri = f"{gitlab_uri}/api/v4/projects/{namespace_urlenc}"
+
+    uri = project_uri + "/registry/repositories"
+    return uri
+
+
+def get_registry_images(uri: str) -> List[Dict]:
+    """
+    List all container images that are currently available in the given GitLab
+    project.
+
+    :param uri: URI pointing to a GitLab instance's image registry
+    :return: list of container image names
+    """
+
+    r = urllib.request.urlopen(uri + "?per_page=100")
+
+    # read the HTTP response and load the JSON part of it
+    return json.loads(r.read().decode())